56 • Fieldbus Coupler 750-337, 750-338
Data
Exchange
WAGO-I/O-SYSTEM
750
CANopen
I
O
1
2
memory area
for input data
I/O modules
input
modules
word 255
output
modules
word 0
word 255
word 0
memory area
for output data
fieldbus coupler
fieldbus
Fig. 3.1-10: Memory areas and data exchange for a fieldbus coupler
g012433e
The coupler process image contains the physical data of the bus modules in a
storage area for input data and in a storage area for output data (word 0 ... 255
each).
1
The input module data can be read from the fieldbus side.
2
In the same manner, writing to the output modules is possible from the
fieldbus side.
3.1.5.4 Addressing
Upon switching on the supply voltage, the data is mapped from the process
image to an object directory (initialization). A CANopen fieldbus master uses
the 16 bit indexes and 8 bit sub-indexes of the object directory in order to ad-
dress the data via the PDOs or SDOs and for access purposes.
Therefore, the position of the data in the process image has no direct meaning
for the CANopen user.
PDO
SDO
I
O
1
2
..
.
Index
Sub-
Index
memory area
for input data
I/O modules
input
modules
word 255
output
modules
word 0
word 255
fieldbus
master
word 0
memory area
for output data
fieldbus coupler
Object directory()
Fig. 3.1-1: Fieldbus specific data exchange for a CANopen fieldbus coupler
g012431e
